


A Study in Veritaserum

by HarrisonHolmes2014



Series: Sherlock Holmes and the Wizarding World [1]
Category: Harry Potter - J. K. Rowling, Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: Auror Greg Lestrade, Aurors, Between the First and Second Wizarding Wars, Canon Divergence - A Study in Pink, Crossovers & Fandom Fusions, F/M, Forbidden Forest, Gryffindor John, Hogwarts First Year, Hufflepuff Molly, Kidlock, Magic, Minor Character Death, POV Third Person Omniscient, Potterlock, Sherlolly - Freeform, Slytherin Pride, Slytherin Sherlock, Super-Smart Molly, Tiny Hint of Mystrade, sort of canon compliant
Language: English
Status: Completed
Published: 2016-05-18
Updated: 2016-05-18
Packaged: 2018-05-22 07:59:08
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 12
Words: 12,710
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6071341
Author URL: https://archiveofourown.org/users/HarrisonHolmes2014/pseuds/HarrisonHolmes2014
Summary: <blockquote class="userstuff">
              <p>On September 1st, 1982, before the "Golden Trio" came to Hogwarts, another group of three friends stepped under its roof. It's Sherlock Holmes' first year at Hogwarts, and almost immediately a mystery presents itself. Several students with no relationship to each other are given dangerously high doses of Veritaserum (Truth Potion) and nearly die while spilling their secrets before the whole school. It's up to Sherlock and his friends, Molly Hooper and John Watson, to figure out who's behind it...and why.</p>
            </blockquote>





	1. Prologue: Chosen By the Wand

**Author's Note:**

  * Inspired by [Choosing](https://archiveofourown.org/works/1940172) by [OwlPost7](https://archiveofourown.org/users/OwlPost7/pseuds/OwlPost7). 



> Book 1 of 7, at least that's the plan (this is gonna take a while, my friends). This story is my first crossover fanfic, so editing suggestions are greatly appreciated!
> 
> Chapter 1, the prologue, was inspired by the beautiful fic "Choosing," written by OwlPost7. I was looking to add more background on Sherlock's wand choosing him, and this story unblocked my ideas. Thank you for the beautiful writing that helped my own story get better.

"Here we are."

With those three words, the slender, dark-haired boy walking down Diagon Alley felt his heart stop for a moment. He gazed up at the peeling gold letters spelling out: "Ollivander's. Makers of Fine Wands Since 382 B.C.E." Sherlock Holmes, eleven, hesitated before crossing the threshold. This was the moment every young witch and wizard dreamed of: being chosen by a wand. The tool that would be a friend and companion all through school and life, and a flawless revealer of the owner's most secret personality traits.

But Sherlock was nervous. His wand, in accord with his passion for experiments, would be different from any other. While most new wand-buyers allowed cores to choose them, Sherlock had supplied his own core. Six months ago his father, a friend of Ollivander's, had taken Sherlock to the wand shop, with Sherlock carrying a batch of thestral tail hairs. Sherlock had not understood why, with centuries of other owners providing cores, he should not be able to bring his. Thestral hair was a highly unique core, with only one wand in history having it, a trait that in his opinion was perfectly suited to him. Plus, though he wouldn't admit to it, the wild thestrals living near the Holmes family country house were, while they were in Sussex, his only friends.

Ollivander had been skeptical. Sherlock well remembered the large silver eyes looking into his own, doubt written all over the wrinkled face. He remembered the wandmaker's retelling of "The Tale of the Three Brothers" (Sherlock's favorite story from Beedle the Bard), and the dangerous wand that had thestral hair as its core. "Such a wand, the only one with a thestral core since the Elder Wand, will require great responsibility...if it even selects you as its partner," he had said.

But Sherlock had not been dissuaded, and after much discussion Ollivander had agreed to make ten wands with the thestral hairs. They'd agreed that if none of them worked, Sherlock would proceed with the regular cores. And now the day was here, the day he would see if his research on wand design and wandlore had paid off. Sherlock was mostly excited, but also a tiny bit afraid. What if the thestral wands, so carefully chosen by him as friends, all rejected him?

Well, there wasn't much time to worry about that. Mycroft, Sherlock's older brother, was getting impatient waiting for the younger one to open the door. Sherlock took a deep breath and listened to the tinkling bell announcing his arrival.

Before Sherlock could adjust to the tingling in his spine, seemingly aroused by the wands, a tall, thin old man emerged from the shop's depths. "Ah, the young Master Holmes," said Ollivander in a voice barely above a whisper. Sherlock shook hands with the old wandmaker, who then greeted Mycroft as well. "And Mycroft! Elm and dragon heartstring, eleven inches, no?"

"Absolutely," Mycroft said smoothly, pulling out his wand. Sherlock smiled at the beautiful instrument, an expression mirrored in Ollivander's face.

"Yes, that was a fine wand. Well suited to such a successful young worker. Already secretary to the Head of Muggle Liason, so I hear from your father!" Mycroft, while dipping his head in acknowledgement, said nothing else, and Ollivander turned to Sherlock. "Well, young Holmes, I have the thestral wands ready for you. Are you ready to test them out?"

Sherlock, though his heart was fluttering with nerves, had no choice but to say yes. Ollivander nodded and brought a small stack of boxes out. Pulling out the first wand, he said, "Try this, then. Hazel wood and thestral tail hair, ten inches, flexible."

Sherlock took the wand and waved it apprehensively. Nothing happened. Ollivander snatched it from his grip and said, "Fir wood, twelve inches, very sturdy." Sherlock let out a cry as the fir wand emitted a stream of angry red sparks.

Holly and rowan, pine and willow...slowly the pile of thestral wands dwindled. Sherlock grew more and more discouraged with each failed wand, but Ollivander seemed more excited the more wands they tried. Finally he opened the tenth box, saying, "Here is the last. Ebony and thestral tail hair, twelve inches exactly, firm. Try it."

The moment the wand entered his hand, Sherlock knew. His palm filled with a sudden warmth, as if the wand itself was made of fire. He raised it above his head and brought it swishing down, and brilliant jets of red and gold light burst from the tip. The wand didn't stop there: when Ollivander asked Sherlock for it, the wand burned its maker's hand and vibrated violently until Sherlock took it back. Though he'd been burned, Ollivander clapped his gnarled, veined hands together, and even Mycroft smiled from his post beside the door.

"Well done, Master Holmes!" Ollivander exclaimed. "Something happened in my shop today that I have never witnessed. Thestral hair, as you know, has only been used for one wand in all of history."

"The Elder Wand," Sherlock said, slightly weary of the endless warnings.

"Yes," breathed Ollivander. "Exceedingly powerful, requiring its true partner to accept his mortality, and highly dispassionate. But your wand...your wand seems to have bonded with you so strongly that another cannot even hold it. It may even, perhaps, reflect your emotions without your wishing it until you are able to control them." He paused. "The fact that a wand of such power and attachment chose someone so - forgive me - young speaks volumes. The Elder Wand, as far as I am aware, never chose a child or adolescent as its partner.

"This wand found a match in you, suggesting you are prepared to deal with its power," said the wandmaker, wrapping the box in silver paper. "With it I believe you will accomplish great things. But be warned: it is difficult to turn one's back on darkness, and power such as this wand offers can be a great temptation towards the shadows. Take great care with it, young Holmes."

With those enigmatic words, Ollivander bowed the two Holmes brothers from his shop.

**Notes for the Chapter:**

> From Pottermore:
> 
> "This jet-black wand wood has an impressive appearance and reputation, being highly suited to all manner of combative magic, and to Transfiguration. Ebony is happiest in the hand of those with the courage to be themselves. Frequently non-conformist, highly individual or comfortable with the status of outsider, ebony wand owners have been found both among the ranks of the Order of the Phoenix and among the Death Eaters. In my experience the ebony wand's perfect match is one who will hold fast to his or her beliefs, no matter what the external pressure, and will not be swayed lightly from their purpose."


	2. King's Cross

A weak ray of autumn sunshine penetrated the clouds hovering over London. Outside King's Cross Station, Sherlock raced through the doors ahead of his family, a blue scarf fluttering behind him. Breathless with excitement, he paused inside the doors and waited for his father to push the heavy, leather-bound trunk inside on a trolley. Brilliant shapes dashed and danced all around him, people hurrying about their business. Besuited businessmen, twin toddlers with golden curls, a woman in a bright red coat, all heading for the same thing he was: a train. The very thought made a little flame of excitement leap up in his chest.

Hogwarts! He was going to Hogwarts! Ever since Mycroft had started, Sherlock had dreamed of this moment. How he'd envied seeing his big brother in swirling black robes, emblazoned with a green-and-silver crest on the left side. He'd yearned to turn a teacup into a bird as his mum did, or make the light blue wallpaper in his and Mycroft's room orange. And how he'd admired the brilliant bursts of light that came from Mycroft's wand when he performed spells. And now he was off to school, to learn all those things, and who knew how much more? Sherlock's own new wand, as Ollivander had said it might, had already given hints of all the knowledge and power that lay before him. Sometimes, if he was angry or very happy, the wand emitted scarlet sparks and bursts of sunshine yellow light. He hoped it would behave itself until he was on the platform; it wouldn't do for Muggles to see it.

"Sherlock!" Mycroft's irritable voice rang out over the din and Sherlock turned to look at his family. Mr. Holmes was pushing a trolley with a heavy trunk perched atop it. Mrs. Holmes and Mycroft followed close behind, her face excited, his impassive. 

_"Please _do not run off. This is a big station, you know," Mycroft scolded.__

__"Yes, Mum," Sherlock said, rolling his eyes. He fell into step beside his brother. Mycroft had mastered the art of dressing like a Muggle, with his crisp dark suit and neatly combed brown hair. As secretary to the head of Muggle Liason at the Ministry, he had to be good at passing for a Muggle. But the light streaming into the station still gleamed off of his lapel pin, a tiny silver and green badge with the words_ Head Boy_ engraved in the metal. Sherlock smiled to himself; Mycroft might be acting grumpy, but he only wore that badge on very special occasions. From this, Sherlock deduced his brother was just as excited for the first year at Hogwarts as he was. 

They had arrived at the entrance, a perfectly normal-looking barrier between platforms nine and ten. Eagerly Sherlock seized the trolley from his father and took the barrier at a run. He glided through as easily as if the bricks were air, and when he looked up his heart seemed to catch in his throat. A long, scarlet steam engine stood waiting, puffing feathery white clouds. Sherlock could almost feel his curls going frizzy with the humidity. Students, some already in their long black robes, rushed back and forth across the platform, and owls' and cats' calls added a layer to the din. As he pulled out the thestral wand, wondering what would happen, it did the strange magic again: bright golden sparks shot from the end as Sherlock drank in the sight of the train.

Behind him, Mycroft and his parents appeared through the gateway. "Oh, good, they're here!" said Mrs. Holmes, waving energetically to someone behind Sherlock. He turned to see who they were meeting, and barely suppressed a groan.

Three people were emerging from the steam cloud, two adults and a short, slight girl with a long, blonde-brown ponytail hanging down her back. The Hooper family joined the Holmeses at the edge of the platform, their greetings and the _smack _of cheek kisses inaudible over the noise. Mr. and Mrs. Hooper stared at the train with wonder in their faces. They were Muggles, and had no inkling that a Wizarding world existed until Molly received her letter. The two fathers walked over to an empty compartment and began loading the trunks. Just behind them, another family group passed towards the train, and Sherlock felt his insides curl: the Donovans, who lived two streets over. Sally caught sight of him and mouthed "Freak" at him while her parents weren't looking. He'd hoped she'd turn out to be a Squib, but fortune was not in his favor, apparently.__

__"Hello, Sherlock," Molly said quietly, not quite looking him in the eye. Already a dull red flush was creeping into the slightly chubby cheeks. Though he was glad for the distraction from Sally, Sherlock refrained from rolling his eyes with great difficulty. The Hoopers had lived three houses down the road since he and Molly were seven, and she'd had a painfully obvious crush on him ever since. Even someone who couldn't deduce like Sherlock and Mycroft could see it. She tended to babble when speaking to him and had a habit of picking at her sleeve, as she did now to her new Hogwarts robes. At least she'd advanced to babbling; until last summer she couldn't even speak to him at all._ _

__Feeling his mother's eyes on him, Sherlock grudgingly replied, "Hello, Molly. Did you like Diagon Alley?"_ _

__"Oh, yes," she said. The corners of her brown eyes crinkled in a smile. "Just think, we're going to do magic! Isn't it wonderful? I have a new wand and everything." She pulled it out. Sherlock, with his new knowledge of wandlore and wandmaking, gave an approving nod at the wand's lovely wood, the deep, rich gold of -__

"Pear wood and phoenix feather," she declared proudly. "Mr. Ollivander said it looks ordinary, but holds a lot of surprises." 

__To escape her yammering, Sherlock said, fully aware of his words' meaning, "Nice. Want me to whip my wand out?" Molly nodded before realizing what he'd said, and she blushed even deeper. Mr. Holmes, who'd overheard the conversation while returning from the train, gave Sherlock a swat in the back of the head._ _

__The train gave a whistle, and Mrs. Holmes shooed the kids towards the train. Unwillingly, Sherlock allowed his mother to plant a kiss on his cheek. "You be good, now," she said. "Make sure you remember to write."_ _

__"And here's hoping you end up in Slytherin," Mycroft said, grinning at last. "God knows that House could use someone who'd give it a better name."_ _

__Sherlock smiled back as he turned to the train. He sensed rather than saw Molly joining him, just behind him, as they climbed aboard. The compartment floor rumbled, the train gave a little jolt, and slowly they began to move. Sherlock waved to his family as they grew smaller, smaller...and finally vanished around the bend._ _

**Notes for the Chapter:**

> Molly's wand wood and core, from Pottermore:
> 
> "This golden-toned wood [pear] produces wands of splendid magical powers, which give of their best in the hands of the warm-hearted, the generous and the wise. Possessors of pear wands are, in my experience, usually popular and well-respected. I do not know of a single instance where a pear wand has been discovered in the possession of a Dark witch or wizard. Pear wands are among the most resilient, and I have often observed that they may still present a remarkable appearance of newness, even after many years of hard use."
> 
> "[Phoenix feather] is the rarest core type. Phoenix feathers are capable of the greatest range of magic, though they may take longer than either unicorn or dragon cores to reveal this. They show the most initiative, sometimes acting of their own accord, a quality that many witches and wizards dislike. Phoenix feather wands are always the pickiest when it comes to potential owners, for the creature from which they are taken is one of the most independent and detached in the world. These wands are the hardest to tame and to personalise, and their allegiance is usually hard won."


	3. Meeting John Watson

For a moment Sherlock stayed at the train window, watching as London flashed past in a whirl of brick and metal. Then he turned to take his seat, virtually walking right over Molly. To his great annoyance, she hadn't been watching the city fly past them.

"How come you're still staring at me?" he asked.

"What? What do you mean, staring?" Molly stammered. But her face was going red again.

"You looked away the second I turned round. Everyone knows that means you were staring."

"Everyone like you, you mean," she corrected. Sherlock almost did a double-take before catching himself. Her tone, strangely, wasn't confrontational, like most people's voices were when they said "like you" to him. It sounded more admiring than anything. Pushing this thought away, he moved into the compartment and took a window seat, facing the direction the train moved so he wouldn't get motion sickness. Predictably, Molly followed him and sat opposite him. "Your mum said I could sit with you, so neither of us is alone."

"Brilliant."

Sherlock thought she caught the sarcasm, for a little crease appeared between her eyes. But the compartment door slid open once more, sparing him further conversation. A rather short yet muscular boy with sandy hair poked his head in.

" 'Scuse me, but is anyone sitting there?" he said, pointing at the empty seat next to Molly. "Everywhere else I've been is full already."

"Oh, no, please come in," Molly said, smiling at him. Looking grateful, the boy dragged a trunk through the door and left it on the floor instead of hoisting it into the compartment above. He set a large cage, holding a handsome barn owl, on the seat beside Sherlock and flopped down next to Molly. As Molly introduced herself, Sherlock studied the boy for a moment, taking in as much as he could as Mycroft had shown him to do.

"Good to meet you," the boy said with a grin. "My name's John Watson." Turning to Sherlock, he added, "So have you got a name, or what?"

"Sherlock. Sherlock Holmes," he answered. "I suppose you're hoping to end up in Gryffindor, or at least your mum hopes you will?"

John started to say "Yes," but paused halfway through, looking confused. "How'd you know that?"

"The sweater, the handmade sweater. It's red, which wouldn't suggest anything if it didn't have that gold trim around the cuffs."

John's light blue eyes went wide, a look Sherlock was accustomed to. "I guess so," he said hesitantly. "My mum was in Gryffindor, so it makes sense. You should be in Ravenclaw, with that sort of brains."

"He'll be in Slytherin, if he has the choice," Molly said, speaking for him. "His brother was in it."

"Who in their right mind would choose _Slytherin?" _said John, shaking his head. "I wouldn't be caught dead in that House. And I thought you seemed okay!"__

_One day my eyes are going to freeze from rolling them so much._ "Being horrible isn't a requirement for being a Slytherin," Sherlock retorted. "Merlin was in it too a long time ago, and you don't hear anyone complaining about him, do you?" 

___"No!" gasped Molly, now staring at Sherlock too. "Really?"_ _ _

___"Yep. So you see," he said triumphantly to John, who looked flabbergasted, "not everyone in Slytherin is an arse."_ _ _

"If you say so." John turned to Molly and the two began chatting about their families. Sherlock heard John and Molly discussing their wands - John's was English oak and unicorn hair - before his mind wandered away; he hated small talk. To avoid the conversation, he pulled _A Beginner's Guide to Beekeeping _out of his pocket and immersed himself in it. Occasionally, he raised his eyes to a brilliant green countryside that shifted constantly, from neat fields and tiny hamlets to deserted moors and dark, tangled woods.__

Far sooner than Sherlock had expected, the Hogwarts Express slowly ground to a halt. All was darkness through the windows, except for a single lamp bobbing towards the train across the platform. Sherlock, John, and Molly squeezed into the flood of students and allowed it to shuffle them out onto the platform. Sherlock could barely contain a gasp: a giant of a man, his face mostly hidden by a tangle of hair and beard, was waving above the sea of heads, calling, "Firs' years, this way, don' be shy! Firs' years over here!" This must be Hagrid, the groundskeeper that Mycroft had told him about. Shyly, a pack of small, generally frightened-looking students broke from the crowd and followed Hagrid to the long-awaited fleet of boats.

Across the Black Lake, into an underground harbor, and up the sweeping, smooth lawns to the castle front doors. All was just as Mycroft and Sherlock's parents had described it, so many times, right down to the stern-faced Professor McGonagall opening the door. Beside him, Sherlock saw John and Molly gazing around at the great stone castle and the darkly waving trees in the Forbidden Forest. John, like him, seemed to have expected what he saw. But Molly was drinking it in, her eyes huge and a smile nearly splitting her face in two.

As they entered the entrance hall, high as a cathedral and lined with shifting portraits, Sherlock felt a smile tugging at his own lips.

**Notes for the Chapter:**

> John's wand wood and core, from Pottermore:
> 
> "A wand for good times and bad, [English oak] is a friend as loyal as the wizard who deserves it. Wands of English oak demand partners of strength, courage and fidelity. Less well-known is the propensity for owners of English oak wands to have powerful intuition, and, often, an affinity with the magic of the natural world, with the creatures and plants that are necessary to wizardkind for both magic and pleasure. The oak tree is called King of the Forest from the winter solstice up until the summer solstice, and its wood should only be collected during that time (holly becomes King as the days begin to shorten again, and so holly should only be gathered as the year wanes. This divide is believed to be the origin of the old superstition, “when his wand’s oak and hers is holly, then to marry would be folly,” a superstition that I have found baseless). It is said that Merlin’s wand was of English oak (though his grave has never been found, so this cannot be proven).
> 
> "Unicorn hair generally produces the most consistent magic, and is least subject to fluctuations and blockages. Wands with unicorn cores are generally the most difficult to turn to the Dark Arts. They are the most faithful of all wands, and usually remain strongly attached to their first owner, irrespective of whether he or she was an accomplished witch or wizard. Minor disadvantages of unicorn hair are that they do not make the most powerful wands (although the wand wood may compensate) and that they are prone to melancholy if seriously mishandled, meaning that the hair may 'die' and need replacing."


	4. Serpent, Badger, Lion

Nervously the first-years clustered closer together in the entrance hall, staring around. Professor McGonagall surveyed them all with sharp, dark eyes like a hawk's. "Welcome to Hogwarts," she said, and instantly the last few murmurs from the first-years dropped off. "The doors you see before you lead into the Great Hall, but before you take your seats, you must partake in the Sorting Ceremony, one of Hogwarts' most treasured traditions. During this ceremony you will be Sorted into your Houses..."

_I know all this. _With this thought, Sherlock tuned out the customary House description and glanced around the entrance hall. It was even more magnificent than he'd imagined. Professor McGonagall's voice seemed to soar high into the dark rafters and come bouncing joyfully back off the stone walls. Sherlock drank in the medieval tapestries draping the walls on either side of the twin marble staircases, especially the one Mycroft had told him about. A tapestry showing a forest scene, with braids of silver thread along the borders, concealed the stairway leading down to the dungeons, and to the Slytherin common room under the lake. Briefly Sherlock imagined himself pushing aside that tapestry.__

__The sound of doors slamming brought Sherlock's mind back to the present. Professor McGonagall had gone into the Great Hall, leaving the first-years alone again. On Sherlock's left, the color had all drained from Molly's heart-shaped face, but she was certainly not alone. Many others, most of them probably Muggleborns, shared her look of abject terror. To his right, John Watson nudged him in the ribs._ _

"D'you reckon it'll be really hard, this Sorting Ceremony?" John asked. "My sister Harriet told me it hurts a lot, but I think she was having a laugh."

Sherlock suppressed a sigh. Did he have "Hogwarts encyclopedia" written across the front of his robes? But, then again, what business did he have keeping knowledge from others? "She was having a laugh," he told John. He could feel Molly's eyes on him and knew she was hanging on to his every word. "The Sorting's just - "

But Sherlock never got to finish, for the Great Hall doors opened and Professor McGonagall led the first-years inside. Sherlock screwed up his eyes: the thousands of candles gleaming off of solid gold plates and goblets drowned their group in a fiery, golden light. He felt hundreds of eyes on him and focused his attention straight ahead, his cheeks feeling warm. Behind him, Molly's breath was quick and short on the back of his neck, and John's face was a little paler than it had been a moment ago.

Finally the group of first-years stopped in front of the Sorting Hat, dirty and ragged on its three-legged stool. As a rip near the brim opened, mouthlike, nerves started to writhe in Sherlock's stomach. It made a strange hum fill his ears so that he could barely hear the hat's song. His wand was acting up again: he could see a sort of puke-green light shining from his pocket.

When the applause died down, he heard Professor McGonagall call the first name, as if from a great distance: "Anderson, Philip!"

A tall, skinny boy with rather large feet staggered out of the group, placed the hat on his head, and waited on the stool. After a moment, the hat shouted, "RAVENCLAW!" As the Ravenclaw table burst into cheers, Philip Anderson removed the hat and practically ran to sit in an empty place on the bench.

Slowly the cluster of first-years dwindled. Sherlock barely attended to the names as they progressed through the C's and D's, into the E's and F's. He noted that while some people were Sorted quickly, others took longer. Sally Donovan, he was glad to see, had to squirm under the hat for almost three whole minutes until it declared her a Gryffindor. But what if the hat never decided with him? The hum in Sherlock's ears grew louder with each name called, until at last - 

"Holmes, Sherlock!"

Sherlock stepped forward, willing himself to put each foot in front of the other as he approached the stool. Hands shaking, he put the hat on his head, sat down, and closed his eyes, breathing in the smell of dust and old leather. He waited.

Then a little voice spoke in his ear. "Hmm...interesting," the hat said. "I see a brilliant mind here, capable of far more than simply good grades. Great powers of observation and memory, that'll do you good. Ah, and a longing to live up to an older example, a brother, a deliciously ambitious streak...I think we have here a tie between two Houses!"

Almost unbidden, the thought came to Sherlock's mind: _I want to be in Slytherin. ___

"Now _that's _a new one," said the hat. "Are you sure? Someone with your mental type would usually be better suited to Ravenclaw..."__

_But I want to use my mind for more than books, more than traditional wit, _Sherlock thought, gripping the edges of the stool very hard._ I want to know_ everything _I'm capable of._

"Very well, then...better be SLYTHERIN!"

Sherlock pulled off the hat and walked to the cheering Slytherin table as fast as he could without running. The wandlight in his pocket briefly changed from puke green to sunshine yellow before it faded. He found an empty seat and sat up a bit straighter as "Hooper, Molly!" was called. Her face white and knees shaking, Molly put the hat on her head - it fell straight down over her eyes - and sat down to be Sorted. The hat seemed to take a while to decide with her, but eventually the rip opened again and it called out, "HUFFLEPUFF!" Sherlock, though he'd suspected she would end up in that House, felt a strange twinge of annoyance as he watched her take her seat, her ponytail swinging as she ran.

The names continued. Sherlock found his attention ebbing away, occasionally catching another name: "Magnussen, Charles...Morstan, Mary...Stamford, Michael..." At last, "Watson, John!" sat on the stool and the hat shouted, "GRYFFINDOR!" almost the minute it touched his head. John dashed to the Gryffindor table, where a fourth-year girl with the same sandy brown hair hugged him.

At last, the Sorting finished with "Yao, Soo Lin!" ("RAVENCLAW!"), and the feast began. Sherlock helped himself to a bit of everything in reach and was one of the first to follow Anthea Greengrass, a Slytherin prefect, into the entrance hall. Feeling eyes on him again, he turned around. John Watson was glancing curiously back at him as he went up the right-hand marble staircase. A moment later, Molly caught his eye from across the hall. As the Hufflepuff Prefect lifted aside the gold and black-trimmed tapestry hiding the stairway to their common room, she gave Sherlock a slightly sad smile. He supposed John Watson had told her Hufflepuffs and Slytherins couldn't be friends on the train; he had a vague memory of hearing something like that.

But as Sherlock descended the stairway into the torchlit dungeons with the other Slytherins, he made a decision. Though the Slytherin-Gryffindor rivalry was common knowledge, he didn't see why he had to obey it. It was unusual, but Sherlock wanted to remain "friends" with the Hufflepuff he knew, and maybe get to know a Gryffindor a little better.

After all, what better way was there to prove how wrong everyone was about Slytherin?


	5. The First Victim

Sherlock's first couple of weeks at Hogwarts passed normally, or as normally as possible for a magic school. He never got lost, as he'd added the stairways and corridors he'd traversed to a room in his mind palace. But that didn't make up for the shock of a ghost drifting through a door he was trying to open, or occasionally running into a mobile suit of armor. His favorite class was, by far, Potions. In his first-ever lesson, he was the only one whose Boil-Reducing Potion looked like Professor Snape's description. At first he'd thought Snape would ignore it, picky as he was about student work, but there were extra emeralds in Slytherin's point-counting hourglass that night. In the evenings Sherlock sat in the Slytherin common room, finishing homework or perhaps reading a book from the library. He adored the constant, soothing swish of lake water, and the occasional glimpses of fish (and once, a mer-girl's wild, yellow-eyed face in the window) through the green.

The biggest surprise for Sherlock was his fellow Slytherins' attitude towards inter-House friendships. The first morning, after finishing breakfast, Sherlock had gone to the Gryffindor table to speak with John Watson. He gave the sandy-haired boy a tentative smile as he walked up, and John glanced at him with surprise. "I didn't expect to talk to you again," he said. "What is it?"

"Just wanted to tell you good luck on our first day of classes," Sherlock said. "Are you nervous?"

John shrugged one shoulder. "Bit, yeah," he said. "But I think we'll learn quick enough. Good luck to you too."

Sherlock did not speak to Molly as he passed the Hufflepuff table, but he returned her shy smile. When he resumed his seat at the Slytherin table, several students quickly looked away as he met their gazes. One third-year boy, who was built along the lines of a troll, scowled at him from across the table. "Why don't you just go join the Gryffindors, then?" he asked, inserting venom into the word "Gryffindors."

"You have a problem with my Gryffindor friend?" Sherlock responded vaguely, not lifting his eyes from his new copy of _Magical Draughts and Potions. ___

__"You're bloody right, I have a problem," growled the boy. "Don't you know Slytherins and Gryffindors aren't supposed to be friends?"_ _

__"Where is that written in the school rules?" Sherlock retorted. "Anyways, this is exactly the kind of behavior that gives us Slytherins a horrible reputation, aren't you aware of that? Don't you want this House to be seen in a better light?"_ _

__"Not if it involves being friends with_ them."_

____"Well, we'll just have to agree to disagree, won't we?" The boy stalked off in a huff, and it wasn't long before the rest of Slytherin House seemed to be taking issue with it. The Slytherins suddenly refused to give Sherlock directions to a new classroom, or to sit near him in the common room. More than once over those first weeks, he heard a hiss of "blood traitor" from the more conservative pure-bloods in his House. He supposed Molly's Muggle parentage must have got round once the other Slytherins saw her speaking to him._ _ _ _

____It would have bothered Sherlock much more had he not had John to talk to. After the awkwardness of that first conversation, things began to open up between the two of them. The Gryffindors and Slytherins had both Potions and flying lessons together, so Sherlock had to endure Sally Donovan's hiss of "freak" more often than he would've liked. But the shared classes also gave him plenty of time to talk to John, which made it bearable. Sherlock learned that John enjoyed Transfiguration, though he wasn't a stellar student, and wanted to try out for Beater on the Gryffindor Quidditch team once they were second-years. John, to his relief, had also been under some fire for befriending a Slytherin._ _ _ _

____"It's stupid," he told Sherlock when they met in the entrance hall one lunch hour, about three weeks into the term. "Most of the other Gryffindors treat me like I'm breaking some sort of rule. Off the Quidditch pitch, why can't a Gryffindor be friendly with a Slytherin?"_ _ _ _

____"I don't get it either," Sherlock said as they entered the Great Hall. Reluctantly, he added, "I guess I'll see you in Potions later."_ _ _ _

____"Sure. See you, Sherlock." John crossed the Hall and sat beside his sister Harriet at the Gryffindor table. Sherlock took a seat at the end of Slytherin's table, by himself as usual, and helped himself to roast pork and peas._ _ _ _

____He was just reaching for a chocolate eclair at dessert when it happened. In front of a hall full of students and professors, a lone sixth-year girl stood up at the Ravenclaw table. Everyone's eyes swiveled onto her; Sherlock was close enough to see a weirdly blank expression on her face.____

______"I was never good at Charms or Potions," the girl said in a toneless, but clear, voice that made the Hall fall silent. "Last year on my O.W.L.s I used a Smart-Answer Quill and that's how I got 'Outstanding' in the exams. I was never...never good at them..."_ _ _ _ _ _

______The girl stammered and shuddered, her chest heaving, and Sherlock could see her shaking. Then her eyes rolled up into her head and she crumpled at the foot of the Ravenclaw table, senseless, and the Great Hall erupted around her._ _ _ _ _ _


	6. Veritaserum

It took several bangs from Professor Dumbledore's wand to restore order. "Prefects," he called, "please lead your Houses back to their dormitories while we take this student to the hospital wing." As benches scraped and hundreds of feet began rumbling out of the Great Hall, the matron Madam Hudson and her assistant, a sixth-year Hufflepuff girl, dashed down from the teachers' table to the unconscious Ravenclaw.

Sherlock was in shock. Why would a perfectly healthy, normal-looking student suddenly reveal a horrible secret and collapse? Taking advantage of the commotion, he slipped unnoticed towards the Ravenclaw table. The teachers had already taken the girl away on a stretcher, magically conjured by Madam Hudson, who gave Sherlock a strained smile when she saw him. But in the crowd, the other teachers hadn't managed to reach the table yet. Carefully, Sherlock took a peek inside the goblet the girl had been drinking from. There was nothing in it but what seemed to be water. Obviously it wasn't water, because there were no pitchers of it at lunchtime. He sniffed it; no odor.

"Holmes!" Professor McGonagall's sharp bark made him jump. "Get back to your dormitory with the rest of your House, or it's ten points from Slytherin!"

Not at all eager to lose points for simple curiosity, Sherlock obeyed her and left the Hall. But he did not go immediately to the green tapestry. Instead, he hovered by the marble staircase, gazing through the herd of students for John Watson. He had a theory, and was eager to share it.

"Sherlock!" Molly Hooper materialized out of the crowd, her face flushed. "Did you just see that?" she exclaimed. "I've never seen anything so weird before! Why would she just _say _something like that in front of everyone?"__

"I hope to figure that out," Sherlock answered, still scanning the crowd for John. "Have you seen that boy John Watson anywhere?"

"No, he's probably back in Gryffindor Tower. Why?"

"I want to ask him something."

"Ask me what?" said a voice. Sherlock and Molly both turned, and John was pushing his way through a knot of excited third-years.

"Oh, good," Sherlock said hurriedly. "Come with me. I want to check something."

Quickly, he turned towards the stairway to the dungeons. He went at a fast walk, desperate to get to his dormitory and see if he was right. To his vague annoyance, Molly trotted along half a pace behind John, but he decided against telling her not to come. Two opinions would be more helpful than one. His mind buzzing, he turned the first corner and went down another staircase.

"Sherlock," Molly panted, "what exactly are we doing?"

"What that girl did wasn't an accident," he replied, ignoring the eyes of portraits following them down the corridor. "No one would just stand up and tell a secret like that to an entire school, teachers and all. She was given something."

"What?" said John, following Sherlock around another corner and into the first torchlit dungeon passage. "What d'you think - "

"We can rule out the kitchen house-elves," Sherlock said. "She had all the same food as everyone else in the Hall. Someone would've had to slip it in her food after it reached the table. But there was a goblet of what looked like water at her place. The Great Hall doesn't serve water with lunch. It was a potion."

Quickly he gave the password to the Slytherin common room ("Pig snout") and led John and Molly inside. They moved so quickly that none of the other Slytherins seated in the dark green velvet armchairs noticed them until they got to the dormitory stairway. The first-year boys' dormitory was blessedly empty, and Sherlock darted to the stack of schoolbooks on top of his trunk. He shuffled through the pile, watched curiously by the other two, until he found what he was looking for: a battered old library book called _An Encyclopedia of Rare Potions and Their Uses. _Running his finger through the contents, he flipped it open.__

__"I got it out of the library to see what things we'll make by the time we're done here," he said, pointing at the potion heading the page. "Read that."_ _

__" 'Veritaserum, English name Truth Potion,' Molly read. 'Properly brewed, Veritaserum will force the drinker to reveal his or her every secret. Physical properties: Clear as water, odorless and tasteless. Warning: Three drops are sufficient. Any larger dose will result in unconsciousness and, in severe cases, death. Signs of overdose: Shortness of breath, swooning, a bitter smell on the lips of the victim. Fatal overdose may be prevented if an antidote (see page 132) is taken within ten minutes of Veritaserum taking effect.' "_ _

__There was silence for a moment. John, Sherlock, and Molly all looked at each other, their faces almost ghostly in the greenish light. Molly's eyes were the size of coins. John asked, "But why would someone do this? What's to be gained by making someone spill their secrets?"_ _

__"Maybe that's not what they're eventually aiming for," Sherlock said grimly, closing the book._ _

__"You think someone wants to_ kill_ people? By making them drink more than three drops of this?" Molly said incredulously. "But...why?" 

____"That," Sherlock said, leading the way out of the dormitory, "is a bloody good question."_ _ _ _


	7. Two More Victims

For several weeks, there were no more incidents with Veritaserum. Sherlock went about his business, keeping his eyes open for any more unusual activity. However, everything was normal. The Ravenclaw girl, it transpired, had drunk two mouthfuls of the potion and had to be transferred to St. Mungo's Hospital for treatment. Rumor had it that her incorrectly won O.W.L. results had been updated and she would have to arrange for career counseling with Professor Flitwick when she returned to school.

"But why would someone do that, Sherlock?" Molly asked him one morning in Herbology a month after the first incident. 

"No idea," Sherlock answered, dumping dragon manure onto Professor Sprout's honking daffodils. He overdid it slightly because he was concentrating on the case, but ignored the flowers' annoyed squawk. "I can't seem to figure it out. Nobody from Slytherin has a grudge against her. John says none of the Gryffindors do either. Did you ask the Hufflepuffs like I asked you to?"

"Yes," Molly sighed, scooping away some of the excess manure with her trowel. She soothed the squawking flowers with one stroke of her hand, something that none of the other first-years had been able to do. "And I asked my friend Soo Lin to check with the Ravenclaws. I hope that was all right."

"Fine. If you trust her, then so can I."

Molly blushed slightly, but said nothing about the compliment. "But no one in either House said anything, or at least they kept it to themselves. And it couldn't have been a teacher...could it?" Her brown eyes grew worried at the thought.

"It's possible. Maybe one of the professors saw her cheating on the exams and didn't say anything."

"But then, why would they wait until now?" Molly said thoughtfully. "Why not just inform the other professors when it happened?"

"I don't know," Sherlock grumbled, helping spread the manure around the daffodils. He hated admitting it. "I guess we'll just have to wait and see if it happens again."

"You don't think it will?" Molly said anxiously.

"It could," he answered. A sneaky little voice in the back of his mind whispered, _I kind of hope it will. _It would be a great little puzzle to solve. Then the bell rang, and he and Molly cleared away their work and separated at the castle door, the Hufflepuffs heading for Charms, the Slytherins for Transfiguration.__

Three days later, Sherlock got his (slightly guilt-ridden) wish. It was lunchtime again, and the Great Hall was particularly rowdy. The first Quidditch match of the school year, Hufflepuff versus Slytherin, had just finished, with a win for Slytherin. Sherlock had not watched the game - he preferred staying inside and reading up on potions to sports - but was more than happy to join in the celebrations with his House. He helped himself to boiled potatoes, watching his classmates and listening to their talk.

Then, he noticed two students climbing onto the House tables, a Gryffindor third-year and a Slytherin sixth-year. Sherlock recognized Herman Wiltshire, the Slytherin Quidditch Captain from all the congratulatory messages he'd gotten. All eyes swiveled onto them, just as they had with the Ravenclaw victim, and Sherlock knew what was going to happen before it did. In the same toneless voice as the Ravenclaw, with the same blank expression, the Gryffindor began talking.

"I took Felix Felicis" - _Liquid Luck, _said a voice in Sherlock's head - "before my final exams last year," said the Gryffindor.__

__"And I," said Wiltshire in the same flat tone, "blackmailed the Hufflepuff Seeker today. That's why...they...lost..."_ _

__Wiltshire's eyes rolled back in his head and he clutched at his throat. Both students collapsed, Wiltshire first, and Sherlock thought he could see the boy's hand scrabbling at the table before he went still. The teachers rushed forward in the mayhem. The Gryffindor was carted off to the hospital wing, but no one seemed able to revive Wiltshire. He too was carried off, but he looked far too still and pale for Sherlock's liking. He wrestled through the crowd down the Slytherin table, to where Wiltshire had been sitting. His suspicions were right: there was a fallen goblet at his seat, with only a few drops of what looked like water in the bottom. Sherlock smiled grimly and scurried away from the table, before Professor Snape saw him._ _

__John Watson and Molly Hooper caught up to him in the Great Hall. "I saw Myrtle's goblet," John panted, his face flushed. "There was water in it. Well, not water, but you know what I mean."_ _

__"Veritaserum," Sherlock said. The three of them exited the entrance hall and walked out into the grounds, where they wouldn't be overheard. "It was in Wiltshire's goblet too. Only his was empty."_ _

__Molly gasped. "Do you think he's..."_ _

__"Dead? Yes," Sherlock said. A shiver went down his spine, but he couldn't tell if it was horror, excitement, or both. "You saw the book. Veritaserum is fatal in large doses. Someone's profiting from these poisonings, and I would love to know who_ and_ what's in it for them." 

____"So what are you saying?" said John slowly. "You want to try and work this out? Why not just let the teachers do it?"_ _ _ _

____"They haven't caught a culprit for the Ravenclaw, have they? And now a student is dead," Sherlock said shortly. "Maybe students can find out things they can't."_ _ _ _


	8. The First Clue

The first flakes of snow began to fall outside Hogwarts and ice on the Black Lake was visible through the Slytherins' windows. Herman Wiltshire's body was stored in the hospital wing, with special charms and potions designed to preserve him until his parents could arrive. By four days after Wiltshire's death, Sherlock was burning with curiosity and an urge to do _something. _The poisoner, now a murderer, had already claimed three victims with his or her Veritaserum. Who was to say that they would stop at that?__

__The heads of Houses came around the Great Hall with sheets, for people to sign up to stay over Christmas. Though Sherlock would've appreciated Mycroft's take on the Veritaserum case, he signed Professor Snape's sheet. Wiltshire's parents were coming for him the first day of the break, two days from now. If Sherlock was going to have a crack at this, he would have to act fast. Seeing Molly waiting for Professor Sprout's sign-up sheet, Sherlock darted over to the Hufflepuff table. He needn't worry about John - he and Harriet were staying too - but he needed Molly on the scene as well. As her father was a mortician, Molly knew a thing or two about bodies._ _

__"Molly," Sherlock said as he came up behind her. She jumped and flushed with pleasure, and before she could greet him he said, "Sign up to stay at Hogwarts over Christmas."_ _

__"What for?" she said, surprised._ _

__Glancing around to make sure they weren't being overheard, Sherlock said in a low voice, "I need your help. I want to have a look at Wiltshire before his parents get him."_ _

__Her brown eyes narrowed slightly. "Even if it weren't against the hospital rules, I'd object," she said stiffly. She blushed even deeper at contradicting him, but both of them ignored this. "I know you want to solve whatever's going on, but don't you think we should have some respect for the dead?"_ _

__Sherlock held back a sigh. "I think your dad would tell you that finding out why someone is dead would be respecting them enough." When Molly still looked doubtful, he said, "Look, you and John and I are the only ones who think this person is a murderer. A_ serial killer,_ Molly," he added. "Out of the three of us, you're the one who knows most about bodies and how they go wrong. We need your help." 

Molly simply looked at him for a moment. Her dark eyes swiveled between each of his, as though she was trying to decide whether or not to trust him. Finally, she said in a resigned voice, "All right. I'll help you and John. I'll write Mum and Dad and tell them I need to stay here for my studies."

"Thank you, Molly," Sherlock said, and he meant it.

That night, after everyone in the Slytherin dormitories had fallen asleep, Sherlock crept out from behind the concealed stone door. He was not easily spooked, but he had to admit the dancing shadows from the torches made his spine tingle slightly. Portraits whispered on the walls, as if they knew he wasn't supposed to be up at this hour (they probably did). It was with some relief that he reached the entrance hall and slipped into an unused classroom next to the Hufflepuff tapestry. Without lighting any torches or his wand, Sherlock sat atop a desk and waited for the others.

John showed up about five minutes after. "Sherlock?" he said tentatively into the dark room.

"Yeah," Sherlock answered quietly. "Now we just have to wait for Molly."

Not a moment later, the door eased open and both boys glimpsed moonlight shining on blonde-brown hair as Molly slipped inside. She lit her wand, and its blue-white glow revealed a grim expression. "I can't believe I agreed to this," she muttered. Glancing to where Sherlock sat on the desk, she said, "I hope you know what you're doing." Her blush was visible even by the low light.

"I always do."

John snorted a little at the arrogance of the statement, but Sherlock ignored both of them. "Now, we need to do this carefully," he said. "Molly and I will look Wiltshire over. John, you stand watch at the hospital door." By Molly's wandlight, he saw the other two nod. "All right, then, let's go."

The walk to the hospital wing didn't take long through the silent castle. Sherlock and John lighted their wands along with Molly, and the wavering beams glinted strangely off the windowpanes as they passed. When they reached the hospital doors, John opened his mouth to unlock them, but Molly gripped his arm. "We should check if Madam Hudson is awake," she said. Pointing her wand at the door, she murmured, _"Homenum revelio." ___

__Nothing happened. When the boys glanced curiously at her, she said, "Spell to reveal live human presence. I found it in a library book doing Charms homework. Madam Hudson and Poppy Pomfrey must be asleep."_ _

__Sherlock thought it best, at this moment, not to discuss the fact that_ Homenum revelio_ was at least an O.W.L. level spell. He tapped the door and whispered, _"Alohomora." _It unlocked with a soft click and the three of them slipped inside. It was dark in the hospital wing, but he could make out the still form underneath a white sheet in the very last bed. Leaving John at the door, he and Molly crept carefully toward it.__

Sherlock pulled back the sheet, revealing the slack, pale face and stiff limbs. Wiltshire was still in his green Quidditch robes. "I don't see anything we don't know already," Molly said softly. "He's been dead several days, and I can smell something bitter on his lips." 

"A sign of a Veritaserum overdose." Sherlock let his eyes wander over the body, taking in as much as he could. Mycroft would've seen more, but Sherlock had to work with what he had. "Mud spatters on the robes. Pine needles along the edges," he muttered. He remembered Wiltshire showing up late to lunch after the game. "Why would he go anywhere near the Forbidden Forest?"

"What about this?" Molly asked, bending closer to Wiltshire's right hand. She picked it up and extended two of the fingers towards Sherlock. Looking carefully, he saw something dark brown underneath the nails. He dug some of the stuff out with his own nail.

"Wood. Treated wood, from furniture, not a tree," he said quietly. A little shiver of understanding passed through his chest. "Come on." He dashed back down the hospital wing and led Molly and John out. Locking the door, he started to turn down the corridor leading to the Great Hall, scene of Wiltshire's death.

But tonight was not to be the night. As the three of them crept down the corridor, a doorknob on the left rattled. A great blur of red and gold shot out of it and halted in front of them. A little man in a belled hat and jester's clothes was hovering about ten feet in the air before them: Peeves, the school poltergeist.

"Weee-eell, what have we here?" Peeves sneered, a malicious little grin on his wide face. "What would Ickle Firsties be doing out of bed so late, hmm?"

"Please, Peeves, shut up, you'll get us all thrown out," Molly pleaded, taking a step towards him. This was a mistake: he swooped down on their heads, blowing through a peashooter as he did. The spitball narrowly missed John and landed with a dull _splat _on the floor.__

"Should go and get someone, I should," Peeves said in a saintly tone. But Sherlock didn't like the gleam in those dark little eyes. "Filch, maybe, he'd know what to do with you lot."

"Get out of our way," snarled John. He pulled out his wand and fired a spell they'd learned in Charms last week at Peeves: _"Furnunculus!" _Immediately the poltergiest's skin began breaking out in angry red boils.__

"STUDENTS OUT OF BED!" Peeves roared, swooping away down the corridor, one hand clutching his face. "STUDENTS OUT OF BED DOWN THE HOSPITAL WING CORRIDOR!"

"Get back to your dormitories!" Sherlock cried at the other two. They didn't need telling twice. The three of them thundered through the corridors to the Entrance Hall, which was mercifully empty. A pang of frustration hit Sherlock at the thought of turning his back on the Great Hall, but Peeves was sure to have woken every teacher and prefect in the castle by now. He pushed aside the Slytherin tapestry and raced down into the dungeons.

It was only in the safety of the common room that Sherlock allowed himself to sit down and think. Gazing into the fire's glowing embers, he remembered the grains of dark wood under the corpse's fingernails. Tomorrow, without fail, he would go to the Great Hall when it was empty. Wiltshire had left a message, and it was up to Sherlock to find out what that message was.


	9. Wiltshire's Last Message

The next day, Sherlock spent most of his time trying to discuss the case with both John and Molly. As the end of term was looming, their joint breaks were taken up with studying and finishing essays. Sherlock was forced to speak to each of them separately, in the classes he shared with them.

He talked to John first, under cover of Charms class. Charms was always a good place to hold a private conversation for a while, as there was generally a lot of action and people didn't notice anything besides successful (and not so successful) attempts. Today's lesson was particularly rowdy: they were learning the Freezing Charm, which rendered its targets immobile for five to ten minutes. They had been given frogs to practice on, which meant that the room was even louder than usual, giving Sherlock plenty of time to discuss his theory with John.

"Molly found wood under Wiltshire's fingernails," Sherlock explained, keeping one eye on the frog. "I think he was trying to carve a message into the Slytherin table the day he was poisoned."

"With his _nails?" _John said incredulously. "Wouldn't that have hurt?"__

"Yes, and your frog's getting away."

_"Immobulus," _John said hurriedly, pointing his wand at the frog. The charm had no effect: the frog merely hopped a few inches further away, forcing John to pick it up. Sherlock concealed a smile; Charms was not John's forte. John continued as if the frog had not tried to make a bid for freedom. "So anyway, it would've hurt, carving something into a table with your nails."__

"What does that suggest to you? _Immobulus." _To Sherlock's great pleasure, his frog instantly froze mid-leap.__

"It was important."

"Good," said Sherlock. "I'm going to try and find out just what Wiltshire thought was so important. Tonight, at eleven, when everyone's in bed."

John had no problem with another nighttime adventure, but Molly was more hesitant. When Sherlock told her during Herbology, she said quietly, "Another night out of bounds? Do you really think that's a good idea, Sherlock?"

"Only time when no one's in the Great Hall."

"But we could lose all our Houses so many points if we were caught," Molly protested. In her anxiety she knocked one of the fruits off of the Abyssinian Shrivelfig she and Sherlock were pruning.

"Careful, Hooper!" cried Professor Sprout from across the greenhouse. Molly muttered an apology, blushing, and resumed her conversation with Sherlock once Professor Sprout was out of earshot.

"We had a really close shave last night, Sherlock," she said quietly. "No one says we'll get lucky again."

"Still, I think solving a murder is more important than winning the House Cup, don't you?"

Molly flushed even deeper. "Oh, all right, you've made your point," she said. "I'm in."

That night, once more, Sherlock left the silent Slytherin dungeon and climbed up through the silent castle. He entered the deserted classroom off the Entrance Hall to find John and Molly both there, looking sleepy but excited at the same time. "All right, let's go," Sherlock muttered, lighting his wand. He led the way into the Great Hall and over to the Slytherin table. "Spread out and see if you can find markings in the table," he instructed the other two. "I can't be sure where exactly Wiltshire was sitting that day." They nodded and the three began the search, their wandlight casting strange, dancing shadows on the stone walls as they moved.

A few minutes later, John spoke in a half-whisper. "Sherlock, I've got it." Sherlock and Molly walked quietly over to where he was standing, a dark outline barely visible by wandlight and the stars shining through the enchanted ceiling. As John and Molly watched, Sherlock bent over the scratches in the wood.

_T-R-U. ___

__Both John and Molly sounded it out quietly. "What does that mean?" John whispered. "Trust?"_ _

__"Truth or true?" Molly suggested. "Maybe he knew it was Veritaserum."_ _

__But neither one seemed to make sense. Sherlock was trying to work it out when a distant set of footsteps broke the silence. John and Molly turned to him, their faces scared in the wandlight. "We have to get back to our dormitories, now," John said. "We shouldn't be here."_ _

__"All right," Sherlock whispered. "Meet me in the entrance hall tomorrow after lunch, both of you. We'll see if we can work this out." Extinguishing his wand, Sherlock led the way out of the Hall and saw the other two on their way back to their dormitories. All the way back to the Slytherins' dormitories, and all as he prepared for bed at last, Sherlock thought about the terminated message. What would a dying person write in their last moments? If it were him, he'd leave some sort of hint as to who was killing him..._ _

__It was only as he was lying down in his own four-poster bed that a quite unexpected word popped into his mind:_ Trunk._


	10. Christmas Investigations

The next morning, Sherlock rose late and read in the common room until lunchtime. Hogwarts Castle seemed to be nearly empty, but the absence of students didn't take anything away from the decorations. A Christmas tree sporting green baubles and silver tinsel stood in a corner in the Slytherin common room, and bunches of holly and mistletoe hung from the ceiling in the corridors. When Sherlock entered the Great Hall, looking for Molly and John, he had to gasp. It looked exactly like a Christmas card, with twelve trees along the walls, their branches strewn with twinkling fairy lights and small, hooting golden owls. He was not a fan of holidays, exactly, but he had to admit this was impressive.

Only a handful of students sat at each House table. After lunch, it was only too easy for Sherlock to catch both John and Molly's eyes and beckon them outside with a turn of his head. They met once again in the abandoned classroom off of the Entrance Hall.

"I thought of something last night," Sherlock said hurriedly as Molly closed the door.

"T-R-U?" asked John, looking excited.

Sherlock nodded. "Wiltshire scratched those letters into the Slytherin table with his fingernails, possibly just after he collapsed from the Veritaserum," he said. "That would've taken a lot of effort for someone dying. So, it must've been important. If you were being murdered, what would be the last thing you'd say?"

"I don't want to die?" Molly suggested. Sherlock nearly rolled his eyes, but refrained from temptation and continued with his theory.

"Wiltshire must've known he'd been poisoned in the last few moments," he said quickly. "What if he was trying to give a hint? What if what he was writing had something to do with the murderer, maybe...a place where we could find a clue?"

"So what was he trying to write, then?" John asked, slightly stumped.

Finally Sherlock's irritation got the best of him. "God, what's it like to not be me? Your brains must be so bored from lack of use." His wand, reflecting his emotions as usual, shot red sparks as he spoke. John opened his mouth to retort angrily, but Sherlock plowed on. "Trunk!" he exclaimed. "Wiltshire was writing the word 'trunk' in the table! That means there might be something in his trunk that leads us to the murderer."

Molly sprang to her feet. Her cheeks were pink with excitement. "How do we get to his trunk?" she asked. "D'you think it's still in his dormitory?"

"Yes, his parents left it to be donated to the Equipment Fund for Students," Sherlock answered, recalling a useful bit of gossip he'd heard in the common room. He raced out of the classroom, Molly and John behind him. Once again, they ran back through the Slytherin tapestry and along the torchlit dungeon corridors. It was quite a bit chillier here than in the castle's upper floors. Sherlock bolted into the common room and hurtled down the stairs into the older Slytherin boys' dormitories. Finding the sixth-years, he thrust the door open and ran inside.

A dark wood trunk with the initials "H.W." stood at the end of the fourth bed. _"Alohomora," _John muttered, and the lock sprung open with a little click. Sherlock heaved it open. It was empty but for a small, crumpled piece of parchment in the far corner. He smoothed it out on the trunk lid and the three of them bent over it. Tight, angled handwriting was scrawled across it in haste.__

_Meet in first clearing in Forest behind groundskeeper's cabin. After Quidditch game. You know what'll happen if you don't._

____Sherlock wouldn't have been able to garner much from the note ordinarily. Only that its writer was a male currently attending or working at Hogwarts, judging from the handwriting style and heavy-duty academic parchment, and that he knew Wiltshire enough to write to him. But Molly plucked at the corner of the parchment, saying "What's this?" as she pulled a tiny white object loose from it. Sherlock, beaming, took it from her and turned to the other two._ _ _ _

____"An owl feather," he said, his voice shaking with excitement. "Don't you see? Whoever murdered Wiltshire must've sent him this by the morning post. There's a threat in the letter, so Wiltshire kept a feather from the owl that brought the note. He planted a clue here for us!"___ _

______"D'you reckon the person who wrote the letter is from Hogwarts?" John asked._ _ _ _ _ _

______"Yes, look at the thickness of the parchment. Only teachers and students use parchment this heavy. All we need to find out now is what kind of owl the writer owned, and we'll be able to track him down."_ _ _ _ _ _

______"Let me see," said Molly. Surprised, but knowing Molly had a knack for magical creatures as well as plants, Sherlock handed her the feather. She lit her wand, so that the green lake light wouldn't affect the feather's natural color, and held it up to her dark eyes. "It's a down feather, too small to be anything else," she muttered. "And it's white, so that narrows it down to a few breeds." Squinting even more closely at it, she said, "Black spots! That must mean it's from - "_ _ _ _ _ _

______"A snowy owl," Sherlock finished for her._ _ _ _ _ _

A quick visit to the Owlery, drafty and glittering with icicles, confirmed it. Among the whirl of brown and gray feathers, there was only one blotch of white. She sat on a perch near the window, where one of Sherlock's fellow Slytherins was sending a handsome tawny owl off with a Christmas card. As the seventh-year student turned away, John read the name on the snowy owl's perch. " 'Agatha. Owner: Jefferson Hope.' " Turning to the others, he said quickly, "We have to tell someone what we know. Today."

"Professor Snape," Sherlock suggested. "He knows me, he'll listen to me. We'll go to his office in the dungeons right after dinner."

But the after-dinner meeting was not to be. Just as Sherlock was returning to the Slytherins' dungeon to get the note for Wiltshire, a ghostly white shape followed him down the corridor. The snowy owl dropped a crumpled piece of parchment at his feet, and he read it by the dim torchlight. In the same tight, angled handwriting it said:

_Sherlock Holmes - Be in first clearing in the Forest behind groundskeeper's cabin. Midnight. I don't need threats with you, I know you'll come to me. ___


	11. In the Forbidden Forest

After receiving the note, Sherlock spent the rest of his day alone in the library. He would've told Molly and John about it, but he knew they would only try to dissuade him from the meeting. But he burned with curiosity, and this might be his only chance to catch Jefferson Hope and turn him in to the teachers. He couldn't risk passing up that chance. 

So after a solitary dinner in the Great Hall, Sherlock pretended to go to bed early. Instead he stayed up, thumbing through _The Standard Book of Spells, Grade 1 _looking for suitable defense spells. There wasn't much he could do as a first-year, but the Freezing Charm, Disarming Charm and Slug-Belching Hex ought to at least help. He practiced each of them a few times in the dormitory, filling the room with flashes of blue and red light, until he was confident he could perform them well enough. As the other Slytherin first-year boys filed in and prepared for bed, Sherlock did the same, a tight wad of apprehension in his chest.__

__At fifteen minutes to midnight Sherlock slipped carefully out of bed and through the deserted common room. Along the dungeon corridors, up the stairs and through the Slytherin tapestry to the Entrance Hall, his heart pounding all the way. Once or twice he thought he heard a soft footstep behind him, but no teachers or prefects appeared from the shadows. Sherlock eased the front doors open and proceeded into the night, his feet making soft crunching noises in yesterday's snow. He slipped into the shadow of the Forbidden Forest, weaving between tall firs and pines, praying that the rumored werewolves in the Forest were asleep or not transformed yet._ _

__The first clearing immediately behind Hagrid's cabin was easy to find. It was the only place near this forest path with a complete covering of snow. Sherlock pulled out the thestral wand, seeing to his displeasure that it was glowing puke-green again._ "Lumos,"_ he muttered, and a blue-white light replaced the green. As long as he kept it lit, his wand wouldn't reveal his fear. Alone in the shadowy clearing, Sherlock waited.

The soft snap of a twig behind him made him spin around. Pointing his wand at the place he'd heard movement, he watched as his adversary came into view. Jefferson Hope was a rather short, stocky boy, but his breadth made Sherlock guess he was a seventh-year. His scarf bore Gryffindor's red and gold. A little clinking noise told him that Hope had some coins in his pockets. His wand, too, was lit and aimed directly at Sherlock's heart.

"Sherlock 'olmes," he said. "What an 'onor to meet you."

"And why would it be an honor to meet a first-year?" Sherlock asked, his voice stronger than his heart.

" 'eard all about you, I 'ave," said Hope. "Word's got round you like solvin' little puzzles. That friend of yours John Watson, tellin' his other first-year friends 'bout you, you 'ad to say it was a bit cute. 'ow've you liked the puzzles I've given?"

"Not all that much, as someone got killed."

"I 'aven't been killin' people, Holmes," said Hope placidly. His blue eyes, cold as the snow at their feet, wrinkled in a little grin. "I just talk to 'em, and they kill themselves." He paused, and Sherlock let the silence stretch, waiting for Hope to come to him. "It's a game I play with people," Hope said quietly. "Want to see 'ow it works?"

"What'll happen to me if I say no?"

Somewhere above their heads, an owl hooted. Hope glanced up in the direction of the sound, pointed his wand into the trees, and said calmly, _"Avada Kedavra." ___

__There was a blinding burst of green light and a weird rushing noise, as if a strong wind had just blasted through the clearing. Sherlock jumped out of the way as the owl toppled down from the trees. Bending over, he saw it was dead. "So that's what you did to the others," Sherlock said, trying to keep his voice from shaking. "Threatened them with the Killing Curse if they didn't meet you." He took Hope's silence as assent. Straightening up, he asked, "What's your game, then? Make me force-feed myself Veritaserum under threat of the Killing Curse?"_ _

__"Bit more interestin' than that." Hope reached into his robes and pulled out two vials. Both seemed to be full of nothing but water. Beckoning Sherlock over, Hope laid them carefully out on a flat rock nearby. "There's a good vial and a bad one, you see," he said, his face still calm. "I'm the only one who knows which is which. I let the others choose which one they want, and I take the other one. And together, in the Great 'all at lunch next day, we both take our...medicine."_ _

__Sherlock stared at the two vials, glittering sinisterly in the moonlight, and did some quick thinking. "But why?" he murmured._ _

__Hope gave a little half-shrug. "Why does anyone do anythin'? To stop from bein' bored."_ _

__"No, I don't think that's it," Sherlock suggested. His heart was pounding, but the promise of a deduction made him calmer. "You walked into the clearing and I heard coins in your pockets. Suggests to me you have an attachment to money. Why else would you carry coins into the middle of a forest, where there's no shops? And," he rambled on, "you've got a lot of coins on you. Someone's paying you to do this."_ _

__"You _are _good," Hope said smoothly. "Not much money in bein' an ordinary ol' student. I s'pose you could say I 'ave a sponsor."___ _

____"Who?" Sherlock said, his attention caught._ _ _ _

____"That's really none of your business, ain't it?" Hope laughed. "But 'e's a bit of a fan of yours, little 'olmes. 'e loved seein' what your brother Mycroft was capable of. Now enough talkin'. Which vial d'you want?"_ _ _ _

____Sherlock stared back at the vials once more. To his delight, the moon caught both of them at just the right angle. It was not for nothing that Sherlock was one of Professor Snape's best students: potions were always at least a little thicker than water. "I'll have the one on the right, please," he said politely, naming the safe one._ _ _ _

____Hope knew it too. Though his face remained impassable, Sherlock saw the lines at the corners of his eyes tighten ever so slightly. "All right, then." Both boys picked up their own vials and uncorked them at the same time. Careful not to smile his delight at solving it, Sherlock raised the water to his lips, and Hope mirrored him with the Veritaserum._ _ _ _

_"EXPULSO!"_

The lone voice ripped through the clearing, and Sherlock ducked as a blaze of blue light soared over his head. Behind Hope, the jet of light hit a massive yew tree, and the tree exploded with a great whirl of leaves and wood. The force of the blast sent Sherlock flying across the clearing and made him slam into an oak on the other side. All around him branches and chunks of the exploded tree fell and were forced across the clearing. Then, as quickly as it had happened, it was silent once more. 

______Shaking, Sherlock rose to his feet. Miraculously, his wand was still in his hand, and he lit it once more. From beneath a massive branch, he could hear a low groan. Pushing the other debris aside, he saw Hope spread-eagled on the ground. Hope's chest rose and fell in agonized breaths. A piece of the yew tree, sharpened from its breaking, was lodged in his shoulder, just above the chest._ _ _ _ _ _

______Sherlock pointed his wand directly at Hope's face. "Tell me who my fan is," he commanded._ _ _ _ _ _

______Why Hope listened to him, Sherlock would never know. But the blue eyes found Sherlock's own, and he mouthed one word before his last breath escaped him._ _ _ _ _ _

______"Moriarty."_ _ _ _ _ _


	12. Case Closed

Sherlock levitated the body of Jefferson Hope and brought him back to the castle. His cursory examination of the clearing revealed little, but he found a second set of footprints in the snow alongside his, a track leading to the clearing and a track returning. He roused Madam Hudson and Poppy at the hospital wing and gave a brief explanation of what happened, and Poppy ran to get Professor Dumbledore. Though he was exhausted and would've loved to get some sleep, Sherlock waited in the hospital wing for the headmaster.

Madam Hudson wrapped a thick blanket around Sherlock's shoulders. "Dear me, you must be freezing," she said. "What on earth would you have been doing in the Forbidden Forest at this hour of the night?"

"Solving a murder," Sherlock answered through gritted teeth. He'd done the right thing, but being out of bounds at night would still lose Slytherin a nice chunk of points. "The person giving people Veritaserum."

Madam Hudson's eyes widened, but she gave no other sign of surprise. "Well, all the same, young man, it would be best to leave something like this to the teachers."

"To idiots," Sherlock muttered, but she pretended not to hear him. She poured a thick potion in a calming shade of sky blue into a goblet. "What's this?" Sherlock asked as she forced it into his hand.

"Calming Draught. For shock, you know."

"But I'm not in shock, I'm - " The rest of Sherlock's protest was cut off by Madam Hudson forcing the goblet to his lips. The moment Sherlock swallowed, he felt a deep sense of soothing calm flood his body. Knowing that was enough, he pushed the goblet away when Madam Hudson tried to make him drink more.

The hospital wing doors shot open, and a whole retinue of people walked in. Professor Dumbledore was at the head, his long silver hair and beard gleaming in the moonlight. Professor Snape was behind him, in his usual black robes, and immediately behind him was Greg Lestrade, Mycroft's friend and, thanks to the older Holmes, an Auror-in-training assigned to Hogwarts. A few moments later, Professor McGonagall and Professor Sprout marched in, leading a pair of very confused and sleepy students: John and Molly. As soon as they saw Sherlock, both of them ran forward to the bed with a whole lot of exclamations and fuss (in Sherlock's opinion). Molly looked very much as if she wanted to hug him, but he was grateful she contained herself in front of all these people.

"Poppy tells me you witnessed the death of a student," Professor Dumbledore told Sherlock, his face grave. "Please explain."

With help from John and Molly, Sherlock told them the whole story. How they had realized the poisoner was using Veritaserum, the examination of Wiltshire's body and the Slytherin table, the note in his trunk and the owl that led them to Jefferson Hope. At that point, Sherlock described the evening's events alone.

"Well, it sounds as if someone followed Sherlock to the Forest and cast the Expulso Curse," said Lestrade, a quill scribbling his words onto a roll of parchment at his side.

"Someone did," Sherlock said, eager to describe his theory about his helper. "There was another trail of footprints beside mine when I left the Forest. Bit of a short, stocky person from the length and shape of their feet. He was a crack shot, that curse came from a distance, but his aim was still perfect under pressure. And he waited until he thought I was in worst trouble before casting a dangerous curse, so strong morals. I think to find him, you should look for someone with nerves of steel and those strong morals, maybe a good candidate for an Auror or Muggle military..."

The words died in Sherlock's throat. He was looking at John, who was listening and nodding appreciatively to what he said. But he could see a very light, nearly dry, line of water around the hem of John's robes and cloak.

"Actually, never mind," Sherlock said, speaking mainly to Lestrade. "Don't listen to anything I just said, I don't know who fired the curse. I'm in shock, you see."

"Very well," said Professor Dumbledore. "Mr. Holmes, you have broken quite the series of school rules, particularly those involving being out of bed after hours. As you know, these transgressions usually result in punishment." He paused, and the corners of his mouth turned up in a smile. "However, as you have brought a murderer to justice through your transgressions, I believe we have cause to be lenient. Severus?"

"I agree," said Professor Snape quietly. "Holmes, I cannot allow you to get out of this completely free, but under the...circumstances...I believe a detention and fifteen points from Slytherin are fair. I will also be writing to your parents and brother tonight, so perhaps you should expect a little more harshness from them." With that, the professors and Lestrade all left the hospital wing.

Molly and John pulled up chairs beside Sherlock's bed. As soon as Madam Hudson and Poppy were out of earshot, Sherlock whispered to John, "Thanks for that, what you did."

Molly looked over at John, wide-eyed. "You?"

"Yeah."

"But..." Molly seemed to be struggling to find words. "You killed Hope when the tree exploded."

John squirmed uncomfortably in his seat. "Yeah, I did," he muttered. "But I didn't think the tree would kill him when it exploded. It was just the first spell that popped into my head." He stopped. Then, as if he couldn't help himself, he said, "But even if I meant to kill him, he wasn't a very nice man, was he?"

"No, I suppose not," Molly said thoughtfully. Glancing at Sherlock, she said, "So will Madam Hudson let you go back to the Slytherin dormitories tonight?"

Sherlock shook his head. "She wants me to stay here tonight, until she's sure I'm not still in shock." He rolled his eyes. "But she said I'd be out for Christmas dinner." Grinning at them, at his two friends, he said, "Who knows? We might have another case before New Year's."

 

The End


End file.
